Most people can sleep without problems after a workout, according to the National Sleep Foundation. / John Fedele, Getty Images

by Kim Painter, Special for USA TODAY

by Kim Painter, Special for USA TODAY

If late night exercise works for you, just do it. That's new advice from a leading sleep group and other experts in sleep and exercise, all of whom say it's time to throw out the old rule that you should never exercise in the hours just before bedtime.

Most people can sleep just fine after a workout, say experts from the National Sleep Foundation, relying on evidence from a growing body of research and a new poll. The 2013 Sleep in America Poll, out today, finds people who exercise at any time of day report sleeping better and feeling more rested than those who don't exercise. It also finds people who exercise in the last four hours before bedtime report sleeping just as well as those exercising earlier in the day.

"The timing of exercise ought to be driven by when the pool's lap lane is open or when your tennis partner is available or when you have time to get away from work, not by some statement that has never been validated," says Barbara Phillips, a University of Kentucky sleep medicine specialist who worked on the poll.

More than half of vigorous and moderate exercisers reported sleeping better on days they exercised - even if it was close to bedtime. In the poll of 1,000 people, just 3% of late-day exercisers said they slept worse. Margin of error was plus or minus 3 percentage points.

The idea that exercise late in the day is bad for sleep was always based on conjecture and anecdote, Phillips and others say. The theory was that the stimulation of exercise, combined with rises in body temperature, would keep people awake.

For some, that may be true, but studies now suggest it's not the norm, says Shawn Youngstedt, a researcher at the University of South Carolina. He also worked on the poll.

Youngstedt conducted one study in which fit young men with no sleep problems rode stationary bikes for three hours and went to bed just 30 minutes later. They slept soundly. Other studies in good sleepers have shown similar results, he says. He is now starting a study of evening exercise in otherwise inactive people who do have sleep problems.

"When I present this data, almost invariably, someone will say, 'I don't care what the data show â?? I think that exercising too close to bedtime is bad for my sleep,' " Youngstedt says. They may be right, he says. But, for many other people, the option of late-day exercise may open up healthy new horizons.

"We have very busy lives now," he says. "For a lot of people evening is the most convenient time."

Jessica Matthews, a fitness instructor and personal trainer who is a spokeswoman for the American Council on Exercise, says her advice has evolved as it's become clearer that different times work for different people. She suggests people who want to try late-day exercise give it go - and play around with the timing, intensity and type of workout to see what feels right.

Some people may still find that they get "more bang for their buck" by exercising early in the day, especially if they can get outside and take advantage of morning sunlight, which can help keep the body clock running on time, says Michael Grandner, a sleep researcher at the University of Pennsylvania and a spokesman for the American Academy of Sleep Medicine.

But any exercise is better than none, for sleep and health, he says. He did not work on the new poll but isn't surprised it found active people sleep best: "Your body is meant to move. Getting the right type and amount of movement helps your body do what it was built to do, and that includes sleeping." Well-rested people also feel more like exercising, so the link goes both ways, he says.

Grandner says data from a larger survey of 150,000 people, conducted by the Centers for Disease Control and Prevention, also found that people who did any exercise, no matter how light, reported significantly better sleep than non-exercisers did.

The foundation poll found:

â?¢ 83% of vigorous exercisers reported very or fairly good sleep quality, vs. 56% of non-exercisers.

â?¢ 67% of vigorous exercisers reported a good night's sleep on all or most work nights, vs. 39% of non-exercisers.

â?¢ Exercisers and non-exercisers reported about the same amount of sleep, just under seven hours a night.